CVE-2026-48523

5.4 MEDIUM

PyJWT is a JSON Web Token implementation in Python

Published: 2026-05-28 · Last updated: 2026-06-01

Severity and scoring

CVSS: 5.4 MEDIUM
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
CWE: CWE-347

Affected products

Vendor	Product
pyjwt_project	pyjwt

Description

PyJWT is a JSON Web Token implementation in Python. From 2.9.0 to 2.12.1, there is a verifier-side algorithm allow-list bypass when jwt.decode() or jwt.decode_complete() are called with a PyJWK key. The token header alg is checked against the caller-supplied algorithms allow-list, but signature verification is performed with the algorithm bound to the PyJWK object instead of the header algorithm. An attacker who controls a registered JWK/JWKS private key can sign with a disallowed algorithm, advertise an allowed algorithm in the JWT header, and still be accepted. The issue affects the documented PyJWKClient.get_signing_key_from_jwt(...) flow. This vulnerability is fixed in 2.13.0.

Source: NVD

References

[NVD]https://nvd.nist.gov/vuln/detail/CVE-2026-48523
[Vendor advisory]https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f
[Vendor advisory]https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f

Related CVEs

Same vendor

CVE-2026-48526 — PyJWT is a JSON Web Token implementation in Python (7.4 HIGH)
CVE-2026-48525 — PyJWT is a JSON Web Token implementation in Python (5.3 MEDIUM)
CVE-2026-48524 — PyJWT is a JSON Web Token implementation in Python (3.7 LOW)
CVE-2026-48522 — PyJWT is a JSON Web Token implementation in Python (4.2 MEDIUM)

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